Earth's Spin Accelerates: Scientists Predict Possible Negative Leap Second by 2029

Scientists have observed that the Earth's rotation is accelerating slightly, leading to days that are a few milliseconds shorter. This seemingly small change has important implications for the global timekeeping system. Traditionally, "leap seconds" are added to atomic clocks to compensate for the Earth's slowing rotation. However, if the current trend continues, experts predict that we may need to subtract a leap second by 2029 – a historic first. This adjustment would signify a major shift in how we synchronize human-made time with the planet's natural rhythms, highlighting the subtle yet dynamic nature of time itself.

The Evolution of Earth's Day Length

The Earth's rotation takes approximately 86,400 seconds, defining a 24-hour day. However, this duration is not constant. Various natural phenomena, ranging from gravitational forces to internal geophysical shifts, cause slight variations in the Earth's spin.

Historically, the Earth’s rotation has gradually decelerated. During the dinosaur era, days were only about 23 hours long. By the Bronze Age, they had increased but were still about half a second shorter than today. Looking ahead, Earth may experience 25-hour days, but scientists estimate that will take another 200 million years.

Implications of the Changing Rotation

Since 2020, the Earth's rotation has been increasing, surprising many scientists. The International Earth Rotation and Reference Systems Service (IERS), based in Washington, D.C., reports that this acceleration continues unabated.

This acceleration results in days that are a few milliseconds shorter. Should this trend continue, experts suggest that a leap second may need to be removed from Coordinated Universal Time (UTC) by 2029. This subtraction would be unprecedented. A leap second is a one-second adjustment to atomic clocks, aligning them with the Earth's irregular rotation.

To date, leap seconds have only been added to compensate for the Earth’s slowing rotation. If the planet spins faster, removing a second from atomic time will ensure that clocks remain synchronized with the actual Earth's rotation.

Shortest Days Expected in July and August 2025

Timeanddate.com forecasts that the trend of shorter days will continue into 2025. Scientists have identified three dates when the Earth's spin is expected to be at its fastest:

• July 9, 2025
• July 22, 2025
• August 5, 2025

Reports from USA Today indicate that on August 5, the length of a day could be 1.51 milliseconds shorter than the standard 24 hours.

Unraveling the Cause of the Acceleration

The exact cause of the recent acceleration remains unclear. Scientists are considering several possibilities:

• Seismic activity
• Changes in Earth's core dynamics
• Glacial rebound (the rising of land after ice melt)
• Shifts in ocean currents or atmospheric pressure

Leonid Zotov, a researcher at Moscow State University, acknowledged that current models cannot fully explain the phenomenon. While changes in the oceans and atmosphere may contribute to variations in the Earth’s spin, they are likely insufficient to account for this significant acceleration. Some researchers suspect that movement within Earth’s molten outer core could be influencing rotational speed.

Reassurance from Scientists

Despite the unusual findings, scientists remain calm. While it is uncommon for the Earth’s rotation to speed up, such fluctuations are not unheard of. Over centuries, the planet still tends to slow down gradually.

The potential removal of a leap second in 2029 is a technical correction to keep atomic clocks aligned with the Earth's rotation. It will not impact daily life, devices, or global operations. However, it serves as a reminder that time is influenced by complex natural forces.